The invention relates to a terminal for a wireless network for a metropolitan area wherein the terminal achieves a transmission rate of multiples of 100 Mbps for an associated wireless link. More particularly, the invention relates to a wireless terminal having a number, n, of digital processing media access control units (MACs) multiplexed to a single radio framer so as to achieve a transmission rate of n times 100 Mbps.
Computers utilized in modern office environments are typically coupled to a local area network (LAN). The LAN allow users of the computers to share common resources, such as a common printer included in the network, and allows the users to share information files, such as by including one or more file servers in the network. In addition, the users are typically able to communicate information with each other through electronic messaging. A commonly utilized type of LAN is Ethernet. Currently, a variety of products which support Ethernet are commercially available from a variety of sources. Other types of LANs are also utilized, such as token ring, fiber distributed data interface (FDDI) or asynchronous transfer mode (ATM).
LANs are often connected to a wide area network (WAN) via a telephone modem. Thus, information is communicated over the WAN via a communication link provided by a telephone service provider. These telephone links, however, are generally designed to have a bandwidth that is sufficient for voice communication. As such, the rate at which information can be communicated over these telephone links is limited. As computers and computer applications become more sophisticated, however, they tend to generate and process increasingly large amounts of data to be communicated. For example, the communication of computer graphics generally requires a large amount of bandwidth relative to voice communication. Thus, the telephone link can become a data communication bottleneck.
Business organizations and their affiliates are often spread over several sites in a metropolitan or geographical area. For example, a business organization can have a headquarters, one or more branch offices, and various other facilities. For such business organizations, LANs located at the various sites will generally need to communicate information with each other. Wireless communication links for connecting local area networks are known. For example, U.S. Pat. No. 4,876,742, entitled xe2x80x9cApparatus and Method for Providing a Wireless Link Between Two Area Network Systems,xe2x80x9d and U.S. Pat. No. 5,436,902, entitled xe2x80x9cEthernet Extender,xe2x80x9d each disclose a wireless communication link for connecting LANs.
Availability is a measure of the average number of errors which occur in digitally transmitted data. An availability of 99.99 percent is commonly required for radio communications. For an availability of 99.99 percent, the average error rate for digitally communicated data must be maintained below 1xc3x9710xe2x88x926 errors per bit, 99.99 percent of the time. The integrity of a wireless communication link, however, is largely dependent upon transient environmental conditions, such as precipitation. Environmental precipitation causes a severe attenuation of the transmitted signal. For example, to maintain an availability of 99.99 in the presence of environmental precipitation, the signal must be transmitted at a level that is 24 dB/km higher than otherwise. Therefore, to ensure an acceptable data error rate under all expected conditions, data is typically communicated over a wireless communication link at a relatively high power and at a relatively low rate. The amount of data required to be communicated over the wireless link, however, can vary widely over time and can vary independently of environmental conditions. In addition, wireless links, especially those operated at high power levels, can cause interference with other wireless links operating in the same geographical area. Thus, the wireless link can become a data communication bottleneck.
Therefore, a technique is needed for efficiently and cost effectively communicating data over a wireless link between Ethernet local area networks.
The invention is a method and apparatus for achieving a data transmission rate of multiples of 100 mega-bits per second (Mbps) in a terminal for a wireless metropolitan area network. In accordance with an aspect of the present invention, a method of communicating data packets in a wireless network includes steps of receiving a first data packet wherein the first data packet is received according to a first rate of data communication, receiving a second data packet wherein the second data packet is received according to a second rate of data communication and wherein the step of receiving the second data packet is performed simultaneously with the step of receiving the first data packet, time division multiplexing the first data packet and the second data packet to a radio frame, and communicating the radio frame via a wireless link wherein the radio frame is communicated at a third rate of data communication wherein the third rate of data communication is equal to at least a sum of the first rate of data communication and the second rate of data communication. The method can also include a step of buffering the first data packet prior to time division multiplexing the first data packet such that the step of buffering the first data packet synchronizes the first data packet to the radio frame. The method can also include a step of buffering the second data packet prior to providing the second data packet to the radio framer such that the step of buffering the second data packet synchronizes the second data packet to the radio frame. The first and second data packets can be received from an Ethernet local area network. The first data packet can be a 100 mega-bit per second (Mbps) Fast Ethernet data packet. The second data packet can be a 10 Mbps Ethernet data packet. The method can include steps of receiving a third data packet, and time division multiplexing the third data packet to the radio frame. The method can include a step of encrypting the first data packet prior to performing the step of time division multiplexing.
According to another aspect of the invention, a method of communicating data packets in a wireless network includes steps of receiving a first Fast Ethernet data packet into a first MAC unit wherein the first data packet is received at a rate of 100 Mbps, receiving a second Fast Ethernet data packet into a second MAC unit wherein the second data packet is received at a rate of 100 Mbps and wherein the step of receiving the second data packet is performed simultaneously with the step of receiving the first data packet, providing the first data packet and the second data packet to a radio framer according to time division multiplexing thereby forming a time division multiplexed radio frame, and communicating the time division multiplexed radio frame via a wireless link wherein the time division multiplexed radio frame is communicated at a rate of at least 200 Mbps. The first Fast Ethernet data packet can be received from an Ethernet local area network coupled to the first MAC unit. The method can include steps of receiving a third Fast Ethernet data packet into a third MAC unit wherein the third data packet is received at a rate of 100 Mbps, and providing the third data packet to the radio framer according to time division multiplexing. In which case, the time division multiplexed radio frame can be communicated at a rate of at least 300 Mbps. The method can include a step of buffering the first data packet in the first MAC unit prior to providing the first data packet to the radio framer. The step of buffering the first data packet can synchronize the first data packet to the radio frame. The method can also include a step of buffering the second data packet in the second MAC unit prior to providing the second data packet to the radio framer such that the step of buffering the second data packet synchronizes the second data packet to the radio frame. The method can include a step of encrypting the first data packet prior to performing the step of providing the first data packet to the radio framer. The method can also include a step of receiving an Ethernet data packet into the first MAC unit wherein the Ethernet data packet is received at a rate of 10 Mbps.
According to a further aspect of the present invention, a terminal for a wireless link in a metropolitan area includes a first data packet receiver for receiving data packets for communication over a wireless link, a second data packet receiver for receiving data packets for communication over the wireless link, a multiplexer having a first input, a second input and an output wherein the first input is coupled to receive the data packets from the first data packet receiver and wherein the second input is coupled to receive the data packets from the second data packet receiver and wherein the output of the multiplexer provides time-division multiplexed data, a packet formatting apparatus coupled to the output of the multiplexer for formatting the time division multplexed data according to radio frames, and a wireless transceiver coupled to the packet formatting apparatus for communicating the radio frames over a wireless link. The first data packet receiver can be a first MAC unit. In which case, the first MAC unit can include a first rate control unit, and a first rate buffer, coupled to the first rate control unit, for temporarily storing data packets received by the first MAC unit such that the data packets are provided to the first input of the multiplexer from the first rate buffers. The first MAC unit can also include a first data encryption apparatus coupled to the first data packet switch. The first MAC unit can include a first data packet switch having a 100 Mbps port wherein the first data packet switch is coupled to the rate control unit. The first data packet switch can be a layer-two switch or a layer-three switch. The first data packet switch can include a 10 Mbps port. The 100 Mbps port can receive data packets from a local area network coupled to the terminal. The second data packet receiver can be a second MAC unit. In which case, the second MAC unit can include a second data packet switch having a 100 Mbps port. The second data packet switch can be a layer-two switch. The second MAC unit can also include a second rate control unit coupled to the second data packet switch, and a second rate buffer coupled to the second rate control unit for temporarily storing data packets received by the second data packet switch wherein the data packets are provided to the second input of the multiplexer from the second rate buffers. The first MAC unit can include a first data encryption apparatus coupled to the first data packet switch. The second MAC unit can include a second data encryption apparatus coupled to the second data packet switch.
According to yet another aspect of the present invention, a terminal for a wireless link in a metropolitan area includes a first MAC unit for receiving Fast Ethernet data packets at a rate of 100 Mbps for communication over a wireless link, nxe2x88x921 additional MAC units for receiving Fast Ethernet data packets at a rate of 100 Mbps for communication over the wireless link, a multiplexer having n inputs, wherein each input is coupled to receive the data packets from a corresponding one of the first MAC unit and the nxe2x88x921 additional MAC units and wherein the output of the multiplexer provides time-division multiplexed data, a packet formatting apparatus coupled to the output of the multiplexer for formatting the time division multplexed data according to radio frames, and a wireless transceiver coupled to the packet formatting apparatus for communicating the radio frames over a wireless link wherein the wireless link has a maximum bandwidth capacity of at least n times 100 Mbps. Each of the first MAC unit and the nxe2x88x921 additional MAC units can include a rate control unit and a rate buffer coupled to the corresponding rate control unit for temporarily storing data packets received by the corresponding MAC unit prior to providing them to a corresponding one of the inputs of the multiplexer. The first MAC unit and the nxe2x88x921 additional MAC units can also include an encryption apparatus coupled to the rate buffer of the corresponding MAC unit for encrypting data packets received by the corresponding MAC unit. The first MAC unit can include a first data packet switch having a 100 Mbps port. The first data packet switch can be a layer-two switch or a layer-three switch. The first data packet switch can include a 10 Mbps port. The first MAC unit can also include a first rate control unit coupled to the first data packet switch, and a first rate buffer coupled to the first rate control unit for temporarily storing data packets received by the first data packet switch wherein the data packets are provided to the first input of the multiplexer from the first rate buffers. Each of the nxe2x88x921 additional MAC units can include a corresponding data packet switch having a 100 Mbps port. Each of the first MAC unit and the nxe2x88x921 additional MAC units can also include a rate control unit coupled to the corresponding data packet switch and a rate buffer coupled to the corresponding rate control unit for temporarily storing data packets prior to providing them to a corresponding one of the inputs of the multiplexer.
An advantage of the present invention is that the maximum transmission rate is limited only by the bandwidth of the wireless link.